1. Field of the Invention
The present invention relates to a sheet punch device for punching the sheet from the copier, the printer, the printing machine, etc., a sheet processing device in which the sheet punch device is provided, an image forming system in which the image forming device, such as the printer, the copier or the facsimile, and the sheet processing device are integrally or separately provided, and a computer program product embodied therein to cause a computer to execute the control function of the sheet punch device in the image forming system.
2. Description of the Related Art
In recent years, small-size, low-cost devices are demanded. Also, in order to provide a small-size, low-cost sheet punch device (also called the punch unit), the DC brush motor has been used as a punching drive motor for the sheet punch device.
On the other hand, the 2-hole/3-hole changeable punch function and the improvement in the punching speed (or the shortening of the punch time) are also demanded. With the provision of such additional functions, the precision of the motor stop in the sheet punch device tends to deteriorate. Hence, there is a need for the improvement in the motor stop precision.
The punch unit or the sheet punch device which uses the rotation drive of a punch motor for the punching power is known. For example, Japanese Laid-Open Patent Application No. 2002-337095 discloses such a sheet punch device. The punch motors used as the power source in the sheet punch device include the punch motor, the brush-less motor, the DC brush motor, etc.
The sheet punch device, disclosed in Japanese Laid-Open Patent Application No. 2002-337095, has the 2-hole/3-hole changeable punch function, and, with the provision of this additional function, the motor drive range with which the punch edge is in the evacuation position (where the punch edge does not project from the lower frame) becomes narrow.
For this reason, if the motor stop precision deteriorates, the punch edge will project from the lower frame at the time of the motor stop, which causes a trouble in the sheet conveyance in the image forming system.
On the other hand, the motors used as the power source in the sheet punch device of this kind include the stepping motor, the brushless motor, the DC brush motor, etc. Among these motors, the stepping motor the amount of rotation of which can be controlled is desirable in order to increase the motor stop precision. However, in order to secure the torque of the motor required for sheet punching, it is necessary to use a large-size stepping motor with which the amount of rotation can be controlled, and the cost of the large-size stepping motor will be raised.
Furthermore, in recent years, the improvement in the punching speed of the sheet punch device is demanded with the improvement in the processing speed of the post-processing device. Also, for this reason, the size and cost of the motor used in the sheet punch device are likely to increase.